The Source for Neurovascular News and Education

June 13, 2024

Key Points:

  • In-Pipeline stenosis relatively common but did not cause symptoms, require new intervention
  • Patency of ophthalmic artery usually maintained with Pipeline

The first study, published online July 21, 2015, showed that in-Pipeline stenosis occurs more often in anterior carotid artery aneurysms and when aspirin is not prescribed, but is often benign. The second study, published July 4, 2015, concluded that ophthalmic artery patency is most often maintained after treatment with Pipeline, though it is important to minimize the number of devices used across the artery.Two studies published online ahead of print in Neurosurgery add to our understanding of the angiographic outcomes associated with use of the Pipeline embolization device in intracranial aneurysms.

In-Pipeline Stenosis Relatively Common at 6 Months 


The Take Home

Though ophthalmic arterial flow compromise and in-Pipeline stenosis occurred in about 10% and 16% of patients, respectively, they typically did not cause symptoms, the authors of the studies say.

For the first study, Pascal M. Jabbour, MD, of Thomas Jefferson University Hospital (Philadelphia, PA), and colleagues analyzed data on 139 patients (mean age 55 years; 85.6% women) treated with the Pipeline device (Covidien) between May 2011 and August 2013 at the Jefferson Hospital for Neuroscience.

On angiographic follow-up at a mean 15.8 months after the procedure, 77% of aneurysms were completely occluded, 13% were near completely occluded, and 10% were incompletely occluded.

Twenty-two patients (15.8%) had in-Pipeline stenosis, which was detected at a mean 6.7 months after implantation. The stenosis was deemed mild (< 50%) in 11 patients, moderate (50%-75%) in 5, and severe (> 75%) in 6. Devices were 100% occluded in 5 patients with in-Pipeline stenosis. All patients were asymptomatic and treated conservatively by restarting or continuing dual antiplatelet therapy.

Stenosis developed in 3 of the 5 patients (60%) who did not receive aspirin due to allergy, but in only 14.2% of those who received aspirin (P = .02).

Aneurysm location played an important role in the finding of stenosis. In-Pipeline stenosis was present in 7.6% of patients with posterior circulation aneurysms and 16.7% of patients with anterior circulation aneurysms (P = .03).

Level of occlusion achieved with the Pipeline device also tended to predict stenosis. Stenosis was found in 7.1% of patients with incomplete aneurysm occlusion and 16.8% of those with complete or near-complete occlusion (P = .09).

On multivariate analysis, having an aneurysm located in the anterior circulation (OR 3.1; 95% CI 1.1-8.8) and not receiving aspirin (OR 10.0; 95% CI 1.4-67.7) were both associated with the development of in-Pipeline stenosis.

Stenosis More Common With Pipeline Than Other Devices

Compared to the Neuroform (Stryker) and Enterprise (Cordis) self-expanding stents, the occurrence of stenosis with Pipeline was considerably more common, Dr. Jabbour and colleagues write. This “suggests that flow diverters likely induce a more robust neointimal response than self-expanding stents.” However, because in-Pipeline stenosis did not cause any symptoms in their study, it “appears to be a mostly benign complication of flow diversion,” they say.

As such, the study authors continue, stenosis “[t]reatment would only be necessary for symptomatic patients and those with resultant infarcts.”

Of particular importance, the authors say, “is that the odds of developing [in-Pipeline stenosis] are 10 times higher when patients have not been pretreated with aspirin.”

As treatment for severe in-Pipeline stenosis, they recommend increasing the dose of aspirin from 81 mg to 325 mg.

Number of Devices Used in Ophthalmic Artery Important

For the second study, Dr. Jabbour and colleagues looked at angiographic data on 95 patients (mean age 53 years; 89.5% women) who received the Pipeline device at their institution. On average, aneurysm size was 8.0 mm. Two devices were required in 14 patients.

At angiographic follow-up an average of 7.5 months after the procedure, the ophthalmic artery was patent in 85 patients, had diminished flow in 4, and was occluded in 6. Overall, 73 patients’ aneurysms were completely occluded, 13 were near completely occluded, and 9 were incompletely occluded. Of the ophthalmic arteries that were covered with 1 device, 8.6% were occluded; 21% were occluded after treatment with 2 devices.

Among patients in the diminished or no flow groups, only 1—whose ophthalmic artery required treatment with 2 devices—developed symptoms. The patient presented with ocular blindness within 6 weeks following the procedure, and angiogram determined that both devices were completely occluded.

On multivariate analysis, decreasing aneurysm size (7 vs > 7 mm) was a predictor of ophthalmic artery patency (OR 1.2; 95% CI 1.1-1.3). There were similar nonsignificant trends for age older than 53 years (OR 1.1; 95% CI 1.0-1.5) and coverage with a single device (OR 1.9; 95% CI 0.9-3.7).

Ophthalmic artery patency, however, was not affected by the level of aneurysm obliteration.

Carotid Artery Injection May Not Be Necessary for All Patients

Because approximately 10% of the patients treated had reduced or no flow in the ophthalmic artery but only about 1% developed any visual symptoms, Dr. Jabbour and colleagues say that Pipeline maintains the ophthalmic artery patency and that arterial flow compromise when it does occur is “usually a clinically irrelevant event.”

“The high rate of [ophthalmic artery] patency after flow diversion is probably secondary to continued physiological demand, although one would expect the rich, distal collateral supply from external carotid branches to increase the tendency for proximal occlusion because distal vasculature can take over supply to downstream branches,” they write.

Due to the low rate of arterial flow compromise, they posit that external carotid artery injection may not be necessary for all patients. “However,” they continue, in certain patient groups with “risk factors, such as young patients with larger aneurysms and in whom it is planned to deploy multiple [Pipelines], external carotid artery injections may be important and may potentially influence the decision to proceed with flow diversion vs other treatment modalities, such as microsurgical clipping.”

Finally, the authors emphasize the “crucial finding” that arterial patency is best preserved when the number of devices used is minimalized.



1. Chalouhi N, Polifka A, Daou B, et al. In-Pipeline stenosis: incidence, predictors, and clinical outcomes. Neurosurgery. 2015;Epub ahead of print.

2. Chalouhi N, Daou B, Kung D, et al. Fate of the ophthalmic artery after treatment with the Pipeline embolization device. Neurosurgery. 2015;Epub ahead of print.



  • Dr. Jabbour reports no relevant conflicts of interest.